Actions

Multiattack. Kostchtchie makes two melee attacks, only one of which can be a bite attack.   Bite. Melee Weapon Attack: +18 to hit, reach 5 ft., one creature. Hit: 13 (1d6 + 10) piercing damage.   Matalotok (Warhammer). Melee Weapon Attack: +18 to hit, reach 10 ft., one target. Hit: 19 (2d8 + 10) bludgeoning damage, or 21 (2d10 + 10) bludgeoning damage when used with two hands, and the weapon emits a burst of cold that deals 10 (3d6) cold damage to each creature within 30 feet of it.

Legendary Actions

Kostchtchie can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. Kostchtchie regains spent legendary actions at the start of its turn.   Attack. Kostchtchie makes one melee weapon attack.   Charge. Kostchtchie moves up to his speed.   Curse (Costs 2 Actions). Kostchtchie curses one creature he can see within 60 feet of him. The cursed creature gains vulnerability to all damage dealt by Kostchtchie until the end of Kostchtchie's next turn.